Fluorescent folic acid-chitosan/carbon dot for pH-responsive drug delivery and bioimaging.

Nowadays, one of the most important reasons of death in the world is cancer. With the development of nanotechnology, advanced methods for treatment of cancer have introduced. In this work, the fluorescent carbon dots (CDs) were prepared from chitosan as the second abundant polysaccharide present in the nature. The surface of CDs was modified with chitosan (CDs/CS) and then the amino groups of chitosan were conjugated with activated folic acid (CDs/CS-FA) for controlled delivery of doxorubicin (DOX) as anticancer drug against HeLa cancer cells. The DOX loading efficiency of fluorescent CDs/CS-FA was high and nearly 60 %. Due to pH sensitive swelling/deswelling of CS, the percentage of cumulative DOX release could reach 90 % at cancer tissue (pH of 5.0) and 52 % at normal tissue (pH of 7.4) within 30 h. The cytotoxicity study revealed that the synthesized CDs were highly compatible on HeLa cells with cell viability 97-88 %. Cellular imaging shows that the entry of CDs/CS-FA to HeLa cells causes a green fluorescence, while the CDs/CS without FA have a negligible fluorescence. These results are due to the important role of FA in cell internalization. Thus, the CDs/CS-FA nanocarrier is suitable candidate for controlled pH sensitive drug delivery and cellular imaging.

A novel ratiometric fluorescence probe based on calix[4]arene functionalized polymer dots for bisphenol A detection in real water samples.

Bisphenol A (BPA) is one of key raw materials used in the production of epoxy resins and plastics, which has toxicological effects on humans by disrupting cell functions through a variety of cell signaling pathways. Therefore, it is of great significance to develop a simple, rapid, and accurate BPA detection method in real water samples. In this study, a ratiometric fluorescence method based on yellow-emitting surface-functionalized polymer dots (PFBT@L Pdots) and blue-emitting carbon dots (Cdots) was described for the detection of BPA. Pdots as the detecting part were synthesized by using highly fluorescent hydrophobic Poly[(9,9-dioctylfluorenyl-2,7-diyl)-alt-co-(1,4-benzo-(2,1',3)-thiadiazole)] (PFBT) polymer and (R)-5,11,17,23-Tetra-tert-butyl-25,27-bis[(diphenylphosphinoyl)methoxy]-26-(3-oxabutyloxy)-28-[(1-phenylethyl)- carbamoylmethoxy]calix [4]arene (L) functionalizing ligand, and Cdots as internal reference were prepared by hydrothermal treatment of citric acid and urea. In the presence of BPA, chemical binding of the phosphorus atoms of nearby PFBT@L Pdots with BPA hydroxyl functional groups led to the aggregation of the PFBT@L Pdots aggregation and quenching their yellow emission, but the blue emission of Cdots, on the other hand, remained stable. The proposed PFBT@L Pdots probe was successfully applied for the detection of BPA in real water samples, and the results were in good agreement with those obtained by HPLC-FLD. To the best of our knowledge, this is the first report that the calixarene has been utilized to modify Pdots.

Identification of High-Yielding Genotypes of Barley in the Warm Regions of Iran.

One of the most important effects of climatic changes is increasing temperatures and expanding water deficit stress in tropical and subtropical regions. As the fourth most important cereal crop, barley (Hordeum vulgare L.) is crucial for food and feed security, as well as for a sustainable agricultural system. The present study investigates 56 promising barley genotypes, along with four local varieties (Norooz, Oxin, Golchin, and Negin) in four locations to identify high-yielding and adapted genotypes in the warm climate of Iran. Genotypes were tested in an alpha lattice design with six blocks, which were repeated three times. Traits measured were the number of days to heading and maturity, plant height, thousand kernels weight, and grain yield. A combined analysis of variance showed the significant effects of genotypes (G), environments (E), and their interaction (GEI) on all measured traits. Application of the additive main-effect and multiplicative interaction (AMMI) model to the grain yield data showed that GEI was divided into three significant components (IPCAs), and each accounted for 50.93%, 30.60%, and 18.47%, respectively. Two selection indices [Smith-Hazel (SH) and multiple trait selection index (MTSI)] identified G18, G24, G29, and G57 as desirable genotypes at the four test locations. Using several BLUP-based indices, such as the harmonic mean of genotypic values (HMGV), the relative performance of genotypic values (RPGV), and the harmonic mean of the relative performance of genotypic values (HMRPGV), genotypes G6, G11, G22, G24, G29, G38, G52, and G57 were identified as superior genotypes. The application of GGE analysis identified G6, G24, G29, G52, and G57 as the high-yielding and most stable genotypes. Considering all statistical models, genotypes G24, G29, and G57 can be used, as they are well-adapted to the test locations in warm regions of Iran.

Evaluation of combined carbon dots and ciprofloxacin on the expression level of pslA, pelA, and ppyR genes and biofilm production in ciprofloxacin-resistant Pseudomonas aeruginosa isolates from burn wound infection in Iran.

OBJECTIVES: Antimicrobial resistance and biofilm formation are increasingly significant public health concerns. This study aimed to examine the antibacterial and antibiofilm properties of carbon dots (C-dots) alone and in combination with antibiotics against biofilm-forming isolates of Pseudomonas aeruginosa. METHODS: The antibacterial property of C-dots was investigated by broth microdilution method against ATCC PAO1 and P. aeruginosa clinical isolates. The antibacterial effect of the C-dots and ciprofloxacin combination was investigated using the checkerboard method. The antibiofilm effect of the C-dots alone and its combination with ciprofloxacin was evaluated using the microtiter plate method. Subsequently, the toxicity of each agent was tested on L929 fibroblast cells. In the end, the effects of C-dots on the expression levels of pslA, pelA, and ppyR genes were determined using real-time quantitative PCR. RESULTS: The combination of C-dots and ciprofloxacin exhibited a synergistic effect. Additionally, this compound substantially decreased bacterial growth (P < 0.0001) and inhibited biofilm formation at MIC (96 µg/mL) and sub-MIC (48 µg/mL) concentrations (P < 0.0053, P < 0.01). After being exposed to C-dots at a concentration of 1mg/mL for 24 hours, the survival rate of L929 cells was 87.3%. The expression of genes pslA, pelA, and ppyR, associated with biofilm formation in P. aeruginosa, was significantly reduced upon exposure to C-dots (P < 0.0023). CONCLUSIONS: The findings demonstrate a promising new treatment method for infections. Furthermore, reducing the dosage of antibiotics can lead to an improvement in the toxic effects caused by dose-dependent antibiotics and antimicrobial activity.

Silanized fiberglass modified by carbon dots as novel and impressive adsorbent for aqueous heavy metal ion removal.

This work discusses the application of a silanized fiberglass (SFG) modified by carbon dots (CDs) as an effective adsorbent for up-taking some heavy metal ions including lead (Pb2+), chromium (Cr3+), cadmium (Cd2+), cobalt (Co2+), and nickel (Ni2+) as pollutant in the aqueous solution by batch method. Removal tests were carried out after optimization of pH, contact time, initial concentration of metal ions, and CDs amount. The SFG modified with CDs (CDs-SFG) was applied for the removal of 10 ppm of each metal ion solution after 100 min and the corresponding results showed the removal efficiencies of 100, 93.2, 91.8, 90, and 88.3% for Pb2+, Cd2+, Cr3+, Co2+, and Ni2+, respectively. The adsorption capacity of CDs-SFG in the metal ion mixed solution was also evaluated, and the results indicated the same trend in the adsorption capacity for metal ions in the mixed solution, though with lower absolute values compared to the single metal solutions. Moreover, the selectivity of this adsorbent for the adsorption of Pb2+ was almost twice of other tested metal ions. The regeneration of the CDs-SFG showed that its adsorption capacity after five cycles was reduced about 3.9, 6.0, 6.8, 6.7, and 8.0% for Pb2+, Cd2+, Cr3+, Co2+, and Ni2+, respectively. Finally, the applicability of the CDs-SFG adsorbent was examined with the analysis of the metal ions in water and wastewater samples.

Identification of Superior Barley Genotypes Using Selection Index of Ideal Genotype (SIIG).

The main objective of the study was to evaluate and select the superior barley genotypes based on grain yield and some pheno-morphological traits using a new proposed selection index (SIIG). For this purpose, one-hundred-eight pure and four local cultivars (Norouz, Auxin, Nobahar, and WB-97-11) were evaluated as reference genotypes in four warm regions of Iran, including Ahvaz, Darab, Zabol, and Gonbad, during the 2020-2021 cropping seasons. The results of REML analysis showed that the heritability of all traits (except plant height) was higher in Gonbad than in other environments, while the lowest values were estimated in Ahvaz and Zabol environments. In addition, among the measured traits, the thousand kernel weight and grain filling period showed the highest and lowest values of heritability (0.83 and 0.01, respectively). The results showed that the seed yield of genotypes 1, 108, 3, 86, 5, 87, 19, 16, 15, 56, and 18 was higher than the four reference genotypes, and, on the other hand, the SIIG index of these genotypes was greater than or equal to 0.60. Based on the SIIG discriminator index, 4, 8, 31, and 28 genotypes with values greater than or equal to 0.60 were identified as superior for Darab, Ahvaz, Zabol, and Gonbad environments, respectively. As a conclusion, our results revealed that the SIIG index has ideal potential to identify genotypes with high yield and desirable traits. Therefore, the use of this index can be beneficial in screening better genotypes in the early stages of any breeding program for any crop.

Water crisis in Iran: A system dynamics approach on water, energy, food, land and climate (WEFLC) nexus.

Water scarcity is a highly complex, multifaceted and dynamic issue, which has become a severe global challenge. Water scarcity is a hyperconnected phenomenon and thus should be studied through nexus approach, however current water-energy-food (WEF) nexus underrepresents the impacts of land use change and climate change on water scarcity. Therefore, this study was investigated to expand the WEF nexus coverage of further systems, improving the accuracy of nexus models for decision-making and narrowing science-policy gap. Current study developed a water-energy-food-land-climate (WEFLC) nexus model to analyze the water scarcity. Modeling the complex behavior of water scarcity enables the analysis of the efficiency of some adaptation policies in addressing water scarcity and will provide suggestions for improving adaptation practices. The results showed that there is a substantial water supply-demand gap in study region, with an excess consumption of 62,361 million m3. Under baseline scenario, the gap between water supply and demand will enlarge, leading to water crisis in Iran as our study region. Climate change was found to be the prime cause of exacerbating water scarcity in Iran, raising evapotranspiration from 70 % to 85 % in 50 years, and considerably increasing the water demand in various sectors. In terms of policy/adaptation measure analysis, the results showed that neither supply-side nor demand-side scenarios could solely address water crisis, and mixed supply-demand side interventions can be the most effective policy to alleviate water crisis. Overall, the study suggests that water resource management practices and policies in Iran should be reevaluated to include a system thinking management approach. The results can be used as a decision support tool that can recommend suitable mitigation and adaptation strategies for water scarcity in the country.

An Authentication-Based Secure Data Aggregation Method in Internet of Things.

Internet of Things (IoT) means connecting different devices through the Internet. The Internet of things enables humans to remotely manage and control the objects they use with the Internet infrastructure. After the advent of the Internet of Things in homes, organizations, and private companies, privacy and information security are the biggest concern. This issue has challenged the spread of the Internet of things as news of the user's theft of information by hackers intensified. The proposed method in this paper consists of three phases. In the first phase, a star structure is constructed within each cluster, and a unique key is shared between each child and parent to encrypt and secure subsequent communications. The second phase is for intra-cluster communications, in which members of the cluster send their data to the cluster head in a multi-hop manner. Also, in this phase, the data is encrypted with different keys in each hop, and at the end of each connection, the keys are updated to ensure data security. The third phase is to improve the security of inter-cluster communications using an authentication protocol. In this way, the cluster heads are authenticated before sending information to prevent malicious nodes in the network. The proposed method is also simulated using NS2 software. The results showed that the proposed method has improved in terms of energy consumption, end-to-end delay, flexibility, packet delivery rate, and the number of alive nodes compared to other methods.

Intrinsic dual-emissive carbon dots for efficient ratiometric detection of Cu2+ and aspartic acid.

Herein, novel intrinsic dual-emitting carbon dots (CDs) are prepared through a one-step hydrothermal treatment of glucose and 3-nitroaniline in sulfuric acid solution and utilized for ratiometric determination of Cu2+ and aspartic acid (Asp). The CDs exhibited an interesting pH-switchable emission behavior displaying an intrinsic dual-emitting peak with emission maxima at 400 and 610 nm at pH 4.0-5.0. The presence of Cu2+ intensively quenched the first emission peak at 400 nm, but it had a negligible effect on the second emission peak. The ratiometric signal displayed a high selectively for Cu2+ over other metal ions and provided a linear response over the concentration range of 0.01-1.00 µM with a detection limit of 7.0 nM. Moreover, at pH 4.0, Asp was able to restore the quenched fluorescence of the CDs-Cu2+ system with a much more successful performance than other amino acids. This on-off-on fluorescence behavior provided a selective ratiometric fluorescence method for the determination of Asp in the concentration range of 0.2-15 µM. The acceptable detection results for Cu2+ in a river water sample (compared to Inductively Coupled Plasma (ICP) method) and for Asp in human serum samples confirmed the potential application of this ratiometric nanoprobe for sensing in real samples.

Should we Leave Nature Unattended or Assist through Enrichment to Foster Climate Change Mitigation? Exclosure Management in the Highlands of Ethiopia.

In order to foster the potential of exclosures to sequester carbon, it is understood that they are increasingly assisted through enrichment planting. To study the impact of the enrichment planting on carbon sequestration process, five exclosures with enrichment planting and five pure naturally regenerated exclosures were selected. Along parallel transects, 20 × 20 m plots were laid at 100 m intervals where all woody vegetations were counted and measured for their diameter and total height. For soil sampling, five subplots at the center and four at each corner of the plots were established. The samples were collected at a depth of 0-0.2 m, and this procedure was repeated for each plot. In this case, when good management practices were implemented (such as Wukro exclosures), significant differences in organic soil carbon above the ground and the total carbon between naturally regenerated and enriched exclosures (P < 0.05) were found. The mean estimates of the above ground carbon, soil carbon, and total carbon were respectively 8.08, 31.04, and 39.12 ton/ha for natural regeneration vs. 7.94, 31.00, and 38.93 ton/ha for enriched regeneration. Lower altitudes had significantly higher soil organic carbon (P < 0.05) than the higher altitudes. However, the slope had an insignificant effect on carbon distribution. Enriched exclosures performed more poorly in carbon sequestration. This was possibly due to the disturbances caused by mass plantation and poor post plantation follow up, since improved performance (P < 0.05) was seen in one enriched exclosure with better management practices.

Aptamer-Based Fluorescent Biosensing of Adenosine Triphosphate and Cytochrome c via Aggregation-Induced Emission Enhancement on Novel Label-Free DNA-Capped Silver Nanoclusters/Graphene Oxide Nanohybrids.

Four fluorescent DNA-stabilized fluorescent silver nanoclusters (DNA-AgNCs) were designed and synthesized with differences in lengths of cytosine-rich DNA strand (as the stabilizing agent) and target-specific strand DNA aptamers for adenosine triphosphate (ATP) and cytochrome c (Cyt c). After their nanohybrid formation with graphene oxide (GO), it was unexpectedly found that, depending on the composition of the base and length of the strand DNA aptamer, the fluorescence intensity of three of the nanohybrids significantly enhanced. Our experimental observations and quantum mechanical calculations provided an insight into the mechanisms underlying the behavior of DNA-AgNCs/GO nanohybrids. The enhanced fluorescence was found to be attributed to the aggregation-induced emission enhancement (AIE) characteristic of the DNA-AgNCs adsorbed on the GO surface, as confirmed evidently by both fluorescence and transmission electron microscopies. The AIE is a result of hardness and oxidation properties of GO, which lead to enhanced argenophilic interaction and thus to increased Ag(I)-DNA complex shell aggregation. Consequently, two of the DNA-AgNCs/GO nanohybrids were successfully extended to construct highly selective, sensitive, label-free, and simple aptasensors for biosensing of ATP (LOD = 0.42 nM) and Cyt c (LOD = 2.3 nM) in lysed Escherichia coli DH5 α cells and mouse embryonic stem cells, respectively. These fundamental findings are expected to significantly influence the designing and engineering of new AgNCs/GO-based AIE biosensors.

Determination of Hg2+ and Cu2+ ions by dual-emissive Ag/Au nanocluster/carbon dots nanohybrids: Switching the selectivity by pH adjustment.

An innovative dual-emissive ratiometric nanohybrid probe comprised of red-emitting a (Ag/Au)@insulin nanoclusters (NCs) and blue-emitting carbon dots (CDs) was designed for sensitive and selective ratiometric determination of Hg2+ and Cu2+ ions.The fluorescence intensity of CDs (λex = 340 nm; λem = 420 nm) was unaffected in the presence of the metal ions tested, whereas the red emitting NCs (λex = 340 nm; λem = 640 nm) was strongly quenched by both Cu2+ and Hg2+ ions. Interestingly, the selectivity of the probe toward these two ions was simply switched by controlling the pH of probe solution without using any chelating agent. The probe selectively responded to Hg2+ ions at acidic condition (pH = 4.0), Cu2+ ions at basic condition (pH = 10.0), and Hg2+-Cu2+ mixtures at pHs within this range. The respective detection limitsfor determination of Cu2+ and Hg2+ ions at their specific pH conditions were estimated as 5 nM and 7 nM, over linear ranges of 20-600 nM and 20-2000 nM, respectively. The fabricated ratiometric probe also showed distinguished fluorescence color changes to visual detection of these ions. Finally, the probe was successfully applied to determination of Hg2+ and Cu2+ ions in tap and mineral water samples.

Resolving the Multiple Emission Centers in Carbon Dots: From Fluorophore Molecular States to Aromatic Domain States and Carbon-Core States.

Despite many efforts focused on the emission origin of carbon dots (CDs), it is still a topic of debate. This is mainly due to the complex structure of these nanomaterials. Here, we developed an innovative method to evaluate the number and spectral characterizations of various emission centers in CDs. We monitored the photostability of a series of column-separated CDs under UV irradiation to obtain three-dimensional data sets and resolve them using multivariate decomposition methods. The obtained results clearly revealed the presence of three different types of emission centers in CDs, including molecular states, aromatic domain states, and carbon-core states so that their single or coexisting appearance was found to be deeply dependent on the reaction temperature. Furthermore, density functional theory and time-dependent density functional theory were used to investigate the electronic and optical properties of some different aza-polycyclic and corannulene molecules as possible polycyclic aromatic hydrocarbons responsible for the above-mentioned aromatic domain states.

Epirubicin-calf thymus DNA interaction: a comprehensive investigation using molecular docking, spectroscopy and fluorescent quantum dots.

Reviewing the mode of interaction between this kind of active pharmaceutical ingredients and DNA has received much more attention in current years. Anthracycline drugs such as Epirubicin are frequently used in cancer treatment for breast cancer treatment. In the present study, the Epirubicin -calf thymus DNA interaction was investigated by using spectroscopic, fluorimetric and molecular docking methods. Water-soluble quantum dots (QDs) with nanometric particle size fabricated and characterized by transmission electron microscope and photon correlation spectroscopy. The binding constant value and the free energy change for this interaction were obtained to be 3.00×106 M-1 and -42.26 kJ mol-1, using the spectroscopic method and docking investigations, respectively. Additionally, fluorescent thioglycolic acid-capped CdTe QDs were used for investigation of EPI and DNA interaction. Epirubicin as a quencher quenched the fluorescence of CdTe QDs after electrostatic adsorption on the surface of QDs. With the addition of DNA, EPI will be desorbed from the surface of CdTe QDs, inserted into the DNA. Subsequently, fluorescence changes of QDs were used for calculation of binding constant value, which was in good agreement with that obtained by the spectroscopic method. By the comparison of the achieved results, the intercalation mode of interaction between Epirubicin and DNA proved.

Green Synthesis of Carbon Dots Derived from Walnut Oil and an Investigation of Their Cytotoxic and Apoptogenic Activities toward Cancer Cells.

Purpose: This paper introduces a green and simple hydrothermal synthesis to prepare carbon quantum dots (CQDs) from walnut oil with a high quantum yield. In addition, cytotoxic and apoptogenic properties of the CQDs were analyzed on human cancer cell lines. Methods: The optical properties and morphological characteristic were investigated by the TEM, XRD, FT-IR, UV-vis and photoluminescence (PL).The cytotoxic potential of walnut CQDs was evaluated on PC3, MCF-7 and HT-29 human carcinoma cell lines using the MTT methods. The mechanism of action was studied by investigating the mode of cell death using the activation of caspase-3 and 9 as well as mitochondrial membrane potential (MMP). Cellular uptake of the CQDs was detected by fluorescence microscope. CQDs had an average size of 12 nm and a significant emission at 420 nm at an excitation wavelength of 350 nm was recorded. Results: The prepared CQDs possessed a good fluorescent quantum yield of 14.5% with quinine sulfate (quantum yield 54%) as a reference and excellent photo as well as pH stabilities. The walnut CQDs were proved to be an extremely potent cytotoxic agent, especially against MCF-7 and PC-3 cell lines. Induction of apoptosis by CQDs was accompanied by an increase in the activation of caspase-3. Caspase-9 activity did not increase after exposure to the CQDs. Additionally; the MMP did not show any significant loss. Conclusion: The results of our study can corroborate the cytotoxic and apoptotic effect of walnut CQDs in the PC3 and MCF-7 cancer cell lines.

Determination of cDNA encoding BCR/ABL fusion gene in patients with chronic myelogenous leukemia using a novel FRET-based quantum dots-DNA nanosensor.

In the present study, we developed a sensitive method based on fluorescence resonance energy transfer (FRET) for the determination of the BCR/ABL fusion gene, which is used as a biomarker to confirm the clinical diagnosis of both chronic myelogenous leukemia (CML) and acute lymphocytic leukemia (ALL). For this purpose, CdTe quantum dots (QDs) were conjugated to amino-modified 18-mer oligonucleotide ((N)DNA) to form the QDs-(N)DNA nanosensor. In the presence of methylene blue (MB) as an intercalator, the hybridization of QDs-(N)DNA with the target BCR/ABL fusion gene (complementary DNA), brings the MB (acceptor) at close proximity of the QDs (donor), leading to FRET upon photoexcitation of the QDs. The enhancement in the emission intensity of MB was used to follow up the hybridization, which was linearly proportional to concentration of the target complementary DNA in a range from 1.0 × 10-9 to 1.25 × 10-7 M. The detection limit of the proposed method was obtained to be 1.5 × 10-10 M. Finally, the feasibility and selectivity of the proposed nanosensor was evaluated by the analysis of derived nucleotides from both mismatched sequences and clinical samples of patients with leukemia as real samples.

A highly sensitive quantum dots-DNA nanobiosensor based on fluorescence resonance energy transfer for rapid detection of nanomolar amounts of human papillomavirus 18.

A very sensitive and convenient nanobiosensor based on fluorescence resonance energy transfer (FRET) was developed for the detection of a 22-mer oligonucleotides sequence in Human Papillomavirus 18 virus (HPV18) gene. For this purpose, water-soluble CdTe quantum dots (QDs) were synthesized and, subsequently, amino-modified 11-mer oligonucleotide as one of the two necessary probes was attached to QDs surface to form functional QDs-DNA conjugates. Right after addition of the QDs-DNA and a second Cyanine5 (Cy5)-labeled 11-mer oligonucleotide probe to the DNA target solution, the sandwiched hybrids were formed. The resulting hybridization brings the Cy5 fluorophore as the acceptor to close proximity of the QDs as donor, so that an effective transfer of energy from the excited QDs to the Cy5 probe would occur via FRET processing. The fluorescence intensity of Cy5 found to linearly enhance by increasing the DNA target concentration from 1.0 to 50.0nM, with a detection limit of 0.2nM. This homogeneous DNA detection method does not require excessive washing and separation steps of un-hybridized DNA, due to the fact that no FRET can be observed when the probes are not ligated. Finally, feasibility and selectivity of the proposed one-spot DNA detection nanobiosensor were investigated by analysis of derived nucleotides from HPV18 and mismatched sequences.

Carbon dots with strong excitation-dependent fluorescence changes towards pH. Application as nanosensors for a broad range of pH.

In this study, preparation of novel pH-sensitive N-doped carbon dots (NCDs) using glucose and urea is reported. The prepared NCDs present strong excitation-dependent fluorescence changes towards the pH that is a new behavior from these nanomaterials. By taking advantage of this unique behavior, two separated ratiometric pH sensors using emission spectra of the NCDs for both acidic (pH 2.0 to 8.0) and basic (pH 7.0 to 14.0) ranges of pH are constructed. Additionally, by considering the entire Excitation-Emission Matrix (EEM) of NCDs as analytical signal and using a suitable multivariate calibration method, a broad range of pH from 2.0 to 14.0 was well calibrated. The multivariate calibration method was independent from the concentration of NCDs and resulted in a very low average prediction error of 0.067 pH units. No changes in the predicted pH under UV irradiation (for 3 h) and at high ionic strength (up to 2 M NaCl) indicated the high stability of this pH nanosensor. The practicality of this pH nanosensor for pH determination in real water samples was validated with good accuracy and repeatability.

Highly sensitive voltammetric sensor based on immobilization of bisphosphoramidate-derivative and quantum dots onto multi-walled carbon nanotubes modified gold electrode for the electrocatalytic determination of olanzapine.

In the present paper, a new bisphosphoramidate derivative compound, 1, 4-bis(N-methyl)-benzene-bis(N-phenyl, N-benzoylphosphoramidate) (BMBPBP), was synthesized and used as a mediator for the electrocatalytic oxidation of olanzapine. The electro-oxidation of olanzapine at the surface of the BMBPBP/CdS-quantum dots/multi-walled carbon nanotubes (BMBPBP/CdS-QDs/MWCNTs) modified gold electrode was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. This sensor showed an excellent electrocatalytic oxidation activity toward olanzapine at less positive potential, pronounced current response, and good sensitivity. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) were determined for olanzapine oxidation, using the electrochemical approaches. Surface morphology and electrochemical properties of the prepared modified electrode were investigated by scanning electron microscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy techniques. The hydrodynamic amperometry at rotating modified electrode at constant potential versus reference electrode was used for detection of olanzapine. Under optimized conditions, the calibration plot was linear in the concentration range of 20 nM to 100 µM and detection limit was found to be 6 nM. The proposed method was successfully applied to the determination of olanzapine in pharmaceuticals and human serum samples.